Modern Vespa

I searched and found some threads, have tried some things and still no luck.

Sunday night, I had the carb out, replaced the float and needle, adjusted my choke cable so it worked correctly. Buttoned it up and put around 15-20 miles on the thing. It ran perfectly. Before that ride, I also had pulled my plug and it was a textbook coffee and cream.

Once warmed up, the bike had been idling a little high, so I dialed down the idle a little and things seemed great.

Rode it to work on Monday, no problems - perfect again.

Yesterday, I left work for lunch and it bogged down and died. Did this a few times before I realized that I was low on gas. Switched to Reserve and it ran good, but then I couldn't keep it idling.

I played with the mixture screw and idle screw, neither seemed to have any affect on how it ran. Pulled the plug and it was fouled black and oily.

Stuck a new plug in and still can't get it to idle. I currently have the mixture screw at 2 turns out and the idle screw at 2.5 turns out (I believe these are the "standard" settings).

Thoughts?

Thank you

You probably had some gunk in your tank when you were on reserve. ( try to avoid using reserve, if you can... all the shitty crud in your tank goes into your carb then. Just fill up more often )

And that gunk has now clogged your idle jet ( or one of your jets anyways ). You had to feather the throttle differently in order to make it run, and that caused the plug to foul.

That's my guess.

Clean your jets again.

yep yep yep

i had the dirty bottom prob and opened my float bowl and ran the tip of my finger in the bowl and sure enough i had gunk

instead of taking care of tank issue i opted for a inline fuel filter

don't do this, i don't care what anybody says

inline filters and 2t's don't mix

either remove tank and clean or replace tank

i replaced the tank and will always do this in the future

*the comfort that i know everything from the pump to my crank is clean and clear is priceless*

Such fickle bitches these machines are...

I'll clean the jets and report back.

Thank you.

i agree with eric. after looking at a petcock and seeing how they are dsigned. its not good to ever use your reserve.

I never really gave much thought to the reserve....

and then i was watching Top Gear last week. It was a cool episode where they raced 3 modes of transport from 1948 : A Vincent Black Shadow motorcycle ( *drool* ), some handmade steam engine train, and a car.

Hammond rode the Vincent Black Shadow and at one point switched it over to reserve. Then he fouled one of the carbs, and it had to be rebuilt on the side of the road.

This made me think that ultimately any vehicle with a reserve setting suffers from the same disease : they all allow the precipitates, dust, grime, and chunks of whatnot to all accumulate at the bottom of the tank. No big deal until you foolishly switch yourself over to reserve and then suddenly your carb becomes gummed up with it all.

It's another reason why i opted to leave the old glass sediment bowl fuel taps ( that they used to use on old vespas ) on both my SS180 and GS160. They're one more line of defense in keeping crud out of your carb. Most taps now just have a mesh filter on top...which promptly falls off because modern taps are so shittily made. At least my glass sediment bowls give me one more collection point to filter off the crud.

Yeah I was all set to clean my rank with navel jelly. On further investigation I will put this off until
the rebuild. It's way rustyer then I thought. I bought the tool also.

I going to pull the tap out clean/ rebuild. Get some bendable furnace cleaning metal brushes. Coat the inside with the the Navel Jelly. Brush it as best I can. Get a small length of metal chain stick it in there close it up thight with duct tape and shake it up baby once a hour or so. Wash it out.
Change out gas& oil lines.

reserve? is that an america only thingy

i was gonna say back off the mixture screw a quarter turn and do a plug chop at roughly one fifth or so throttle

No... it's a universal, but pre-fuel gauge thingy.

Well, no luck.

I've had the carb out twice. Cleaned the entire carb, paying close attention to the jets.

No different. Idle screw doesn't seem to affect it at all...

Thoughts?

Is it possible that my fuel tap is now gummed up too and is limiting my fuel flow? Would this contribute to the issues I'm seeing?

Is it possible to clean the tap?

When you cleaned the carb, did you run a small wire through the little brass spigot that points downward into the venturi?

Yes, it could be possible your tap got gummed up ..you could always disconnect the fuel hose and see how quick it flows into a 2 liter bottle or something.

No, I blasted the jets with carb cleaner and compressed air. As for the venturi spigot, I blasted carb cleaner in the jet slots after they were removed. This then came streaming out there.

That could be the culprit, I'll dig around in there tonight.

you MIGHT be ok with what you did. But that brass spigot is an oft-forgotten thing to clean.

It's a little more clog-prone on the old models. I think the P-series had a single large downward hole instead of several smaller ones that were more readily clogged.

I'll check it again, because I still can't get it to idle after the cleaning.

Figured it out - my choke cable isn't operating correctly. When closed, it's not closing the choke all of the way.

I've had more problems with that choke cable sticking and working correctly.